激光支持的脉冲等离子体推力器工作过程实验研究

Experimental Study on Operating Process of Laser-Assisted Pulsed Plasma Thruster

关键词:  脉冲等离子体推力器  高速摄影技术  电磁加速机制  附着等离子体电弧  初始电压

Key words:  Pulsed plasma thruster  High-speed photography technology  Electromagnetic acceleration mechanism  Attached plasma arc  Initial voltage

摘要:

为了加深对激光支持的脉冲等离子体推力器工作过程的认识，对有无陶瓷隔离板和不同初始电压下的激光支持的脉冲等离子体推力器进行了实验研究。利用放电伏安特性对比了放电特性参数和性能参数，然后利用结合窄带滤光镜的高速摄影技术揭示了性能差异背后的物理过程变化。结果表明，陶瓷隔离板可以有效避免放电电弧对工质的烧蚀，这可以抑制滞后烧蚀的产生，从而提高推力器的推进性能。对激光烧蚀产生的工质的电离和加速是在多次振荡放电过程中进行，而不像理想电流片模型那样只电离和加速一次。放电通道内工质的电离和加速效果最为显著的时间为放电的第2个半周期。随着初始电压的增加，单位放电能量产生的推进性能先增加后趋于平稳，然后继续增加。单位放电能量产生的推进性能在初始电压高于2050V后得到较大的提高，通过放电等离子体图像推测，这意味着附着等离子体电弧的存在对推力器性能的提高有重要影响。

Abstract:

In order to deepen the understanding of the operating process of the laser-assisted pulsed plasma thruster （LAPPT）， the LAPPT with or without ceramic separator and at different initial voltages were experimentally studied. The discharge characteristic parameters and performance parameters were compared by using the discharge volt-ampere characteristics. Then the physical process changes behind the performance differences were revealed by using high-speed photography techniques combined with narrowband filters. The results show that the ceramic isolator can effectively avoid the ablation of propellant by discharge arc， which can inhibit the generation of late-time ablation and improve the propulsion performance of thruster. The ionization and acceleration of the propellant produced by laser ablation is carried out in the process of multiple oscillation discharges， rather than only ionization and acceleration once as in the ideal current sheet model. The most significant time of ionization and acceleration effects of propellant in discharge channel is the second half cycle of the discharge. With the increase of initial voltage， the propulsion performance generated by unit discharge energy increases first and then tends to be stable， and continues to increase afterwards. The propulsion performance generated by unit discharge energy is greatly improved when the initial voltage is higher than 2050V. It is inferred from the discharge plasma image that this means that the presence of attached plasma arc has an important effect on the performance improvement of the thruster.